The present invention relates to a vehicle seat and more particularly, relates to a vehicle seat intended for use in a motor vehicle such as a motor car.
It has been appreciated that if a motor vehicle, such as a motor car, is involved in a rear-end collision, or rear impact,xe2x80x94that is to say if a following vehicle runs into the back of the carxe2x80x94the occupants of the struck car often suffer from neck injuries.
It is to be understood that during a rear-end collision of this type, the vehicle that is struck is subjected to a forward acceleration. This imparts a forward acceleration to the seats of the vehicle. The squab and the back of each occupied seat engage the posterior and torso of the occupant of the seat and impart a substantial acceleration to the posterior and torso of the occupant. However, no corresponding acceleration is immediately imparted to the head of the occupant. The head is a part of the body that has substantial mass, and consequently the head has substantial inertia.
Thus, whilst the posterior and torso of the occupant of the vehicle are accelerated forwardly as a result of the rear-end collision, the head of the occupant of the vehicle initially remains stationary. This causes the neck initially to adopt a xe2x80x9cSxe2x80x9d-shaped configuration as the lower part of the neck moves forwardly, whilst remaining vertical, and the upper part of the neck remains in its initial position. Subsequently, the head begins to rotate, and the neck then occupies a curved configuration. The head subsequently moves forwardly. Research has shown that xe2x80x9cwhiplashxe2x80x9d injuries may occur when the neck adopts the xe2x80x9cSxe2x80x9d-shaped configuration, if the head is moving, relative to the torso, at a substantial speed.
The present invention seeks to provide an improved vehicle seat in which the risk of xe2x80x9cwhiplashxe2x80x9d injuries occurring to the occupant of the seat during a rear-end collision are reduced.
According to this invention there is provided a vehicle seat, the seat comprising an inner framework; the inner framework defining a first portion to be received within the squab of a seat and second portion to be received within the back of a seat, the second portion being mounted on the first portion for rearward pivotal movement about the predetermined pivotal axis; there being a damper, together with dampening mechanism providing a mechanical advantage, connected between the first portion and the second portion, to dampen said rearward pivotal movement; the dampening mechanism providing the mechanical advantage being disposed so that as the second portion of the frame moves rearwardly, pivotally relative to the first portion, the mechanical advantage changes so that the dampening effect increases.
Preferably the damper comprises a gas spring.
Conveniently the dampening mechanism providing a mechanical advantage comprises a pivotally mounted lever arm element comprising two lever arms, one lever arm being connected to the damper, and the other lever arm being connected to a component which moves in response to said rearward pivotal movement of the second framework portion about the predetermined axis.
Advantageously during pivotal movement of the lever arm element as a consequence of rearward pivotal movement of the second framework portion about said predetermined pivotal axis, the effective length of one lever arm reduces, and the effective length of the other lever aim increases to provide the said change in mechanical advantage.
Preferably said one pivotal arm is connected to the said component which moves in response to said rearward pivotal movement of the second framework portion about the predetermined pivotal axis by means which move axially of the lever arm as the lever arm element moves pivotally.
Conveniently the first lever arm defines an elongate substantially axially extending slot and the said component carries an element engaged with the slot, which move axially along the slot as the lever arm element moves pivotally.
Preferably the lever arm element is pivotally mounted on a support plate, the said component which moves in response to rearward pivotal movement of the second portion of the framework about the predetermined pivotal axis, also being pivotally connected to the fixing plate to define said predetermined pivotal axis.
Advantageously the component comprises a fixing plate carried by a recliner mechanism, the recliner mechanism having another fixing plate which is connected to the second portion of the framework adapted to be received within the back of the seat.
Preferably the back of the vehicle seat is provided with a head-rest support frame, an elevating mechanism being provided to cause the head-rest support frame to move to an elevated position, relative to the back of the seat, in response to said rearward pivotal movement of the second portion of the framework about the predetermined pivotal axis.
Conveniently the elevating mechanism provided to move the head-rest support frame to the elevated position comprises a Bowden cable, the core of which is connected to move the head-rest support frame upwardly against a spring bias when the core of the cable is subjected to tension, and a tension mechanism to subject the core of the cable to tension in response to rearward pivotal movement of the back of the seat about the predetermined pivotal axis.
Advantageously the core of the Bowden cable is connected to a lever, the lever also being connected to at least one Bowden cable having its core connected to parts of a mechanism which move relative to fixed points in a rearward pivotal movement of the back of the seat about the predetermined pivotal axis, with the core of the Bowden cables being connected to said fixed point.
In order that the invention may be more readily understood and so that further features thereof may be appreciated, the invention will now be described, by way of example, with reference to the accompanying drawings in which: